1. Field of the Invention
The present invention relates to an electrical connector assembly which comprises an electrical connector and a pick up cap, the pick up cap being mounted onto the connector for providing a plane top surface to be engaged by a vacuum suction device, whereby the connector assembly can be moved onto a circuit substrate such as a printed circuit board (PCB) on which the electrical connector is to be mounted.
2. Description of the Prior Art
As electronics technology continually develops, manual assembly in mass production facilities is being steadily replaced by automatic assembly. In general, automatic attachment of an electrical connector to a printed circuit board (PCB) involves a vacuum pick up device that picks up the electrical connector from one position and places it in another position. U.S. Pat. Nos. 6,413,111, 5,681,174, 5,651,684, 5,249,977 and 5,026,295 show that the electrical connector needs to have a plane top surface in order for it to be reliably engaged by the vacuum pick up device. An article entitled “MicroPGA Packages” (CONNECTOR SPECIFIER, May 2000, pp.16˜18) discloses an electrical connector for an electronic device. The connector defines a rectangular through hole in a center thereof for dissipating heat produced by the electronic device. Therefore, the connector cannot be directly engaged by a vacuum pick up device. Generally, the connector is provided with a pick up cap, so that the combination can be engaged by the vacuum pick up device.
Referring to FIGS. 7 and 8, a conventional electrical connector assembly 6 comprises an electrical connector 8 and a pick up cap 9 mounted on the connector 8. The connector 8 comprises an insulative housing 80 and a multiplicity of electrical terminals. 81 received therein. The housing 80 is substantially a rectangular substrate, and is formed from dielectric material such as LCP (liquid crystal polymer) that can endure soldering temperatures. The housing 80 comprises a rectangular cavity 801 in a middle portion thereof, for receiving an electrical package, such as a central processing unit (CPU) therein, and a pair of opposite lateral sidewalls 800. A multiplicity of terminal-passages 803 is defined in a portion of the housing 80 around the cavity 801, for receiving a corresponding number of the terminals 81 therein. Two latching protrusions 8000 are defined in respective outside of the sidewalls 800 in a middle thereof. A cross-section of the latching protrusion 8000 is generally triangular.
The pick up cap 9 mounted on the electrical connector 8 includes a base portion 91 having a plane top surface, and first and second extending portions 92, 93 extending from opposite ends of the base portion 91 respectively. The first and second extending portions 92, 93 and the base portion 91 are formed on the pick up cap 9 in alternate fashion, for being received on the two opposite lateral sidewalls 800 respectively. The first extending portion 92 comprises two parallel first arms 920, for being received in the sidewall 800 of the housing 80. The second extending portion 93 comprises two parallel second arms 930, for being received in the other sidewall 800 of the housing 80. A connecting portion 921 interconnects distal ends of the first arms 920, for facilitating a user in releasing the pick up cap 9 from the connector 8. A pair of first clasps 922 depends from distal ends of the first arms 920 respectively. A first latching arm 923 interconnects distal ends of the first clasps 922. The two first clasps 922 and the first latching arm 923 cooperatively define a first socket 924 therebetween, for receiving the latching protrusion 8000 of the housing 80 therein. A pair of second clasps 931 depends from distal ends of the second arms 930 respectively. A second latching arm 932 interconnects distal ends of the second clasps 931. The second clasps 931 and the second latching arm 932 cooperatively define a second socket 933 therebetween, for receiving the other latching protrusion 8000 of the housing 80 therein.
In assembly, the pick up cap 9 is placed on the connector 8, with the first and second latching arms 923, 932 loosely resting on the corresponding sidewalls 800 respectively. Then, the pick up cap 9 is pressed down. The first and second latching arms 923, 932 deflect outwardly The first and second latching arms 923, 932 respectively rides along an outer face of the latching protrusions 8000 until the latching protrusions 8000 are received in the first and second sockets 924, 933 respectively. The pick up cap 9 is thereby securely mounted onto the connector 8. A nozzle of the vacuum suction device (not shown) can then engage the plane surface of the base portion 90, in order to move the connector assembly 6 to a desired location on the PCB.
In the above-described assembly process, the latching protrusions 8000 are formed on respective outer faces of the sidewalls 800, and are engaged in the first and second sockets 924, 933. When the pick up cap 9 is detached from the housing 80, a user applies force on the connecting portion 921 of the pick up cap 9, which is typically in an inclined direction as indicated by arrow F in FIG. 8. Force F comprises the component force Fx acting along a direction parallel to the pick up cap 9, and the component force Fy acting perpendicularly upwardly relative to force Fx. The effect of force Fx is to make the engagement between the pick up cap 9 and the housing 80 tighter. As a result, it is difficult to detach the second latching arm 923 from the corresponding latching protrusion 8000. The force F applied on the connecting portion 921 needs to be considerable in order to be able to detach the pick up cap 9 from the connector 8.
Thus, there is a need to provide a new electrical connector assembly that overcomes the above-mentioned disadvantages.